Thank God you guys weren't around when hot rodding was just getting started... we'd all be discussing how to get better fuel economy out of our Maxwells.
Oddball swaps were "fine" when better options were not available......AKA early Ford pickups. Of COURSE you swap something, anything, into that!!!
50's Chev anything.........no........V's..........available.........So put in a Cad, Olds, Poncho, hemi. ANYTHING including a Chev SB or '09
But in this case engines are plentiful, and he won't be gaining anything pricewise OR performancewise, that he could not easily and inexpensively do with that AMC. There is nothing wrong with that AMC, lots of Jeepers would LOVE to score that thing